1. Field of the Invention
This invention relates generally to improvements in rate of penetration recorders and, more particularly, but not by way of limitation, to a rate of penetration recorder having a latching control circuit for preventing the production of erroneous output signals.
2. Description of the Prior Art
In drilling wells for the discovery and production of oil, water or the like, it is often of critical importance to know the precise depth of the drill bit, as well as the time at which the depth was attained. In accomplishing this data acquisition, various devices have been designed, and are generally referred to as rate of penetration recorders. A number of such prior art devices are disclosed in the following U.S. Pat. Nos.: 3,541,852, issued to Brown et al.; 3,777,560, issued to Guignard; and 3,853,004, issued to Westlake et al. Related apparatus of more general interest to the subject invention are disclosed in the following U.S. Pat. Nos. 2,322,478, issued to Scherbatskoy; 2,330,752, issued to Sikes, Jr.; 2,330,753, also issued to Sikes, Jr.; 2,539,758, issued to Silverman et al.; 2,688,871, issued to Lubinski; 2,957,346, issued to Knight; 3,374,669, issued to Redwine; 3,522,727, issued to Calhoun; 3,620,077, issued to Brown et al.; 3,785,202, issued to Kelseaux et al.; 3,881,695, issued to Joubert; 3,891,038, issued to Delestrade et al.; 3,898,880, issued to Kelseaux et al.; and 3,391,735, issued to Guignard. Various other types of measuring devices used in well drilling are disclosed in the following U.S. Pat. Nos.: 2,166,212, issued to Hayward; 3,027,649, issued to Sloan; 3,368,400, issued to Jorden, Jr., et al.; 3,490,150, issued to Whitfill, Jr.; 3,643,504, issued to Rundell; 3,651,871, issued to Greene; 3,660,649, issued to Gilchrist; 3,752,966, issued to Foy, Jr., et al.; and 3,912,684, also issued to Rundell.